Meningiomas of the cranial base

Summary Treatment objectives for meningiomas of the cranial base include relief of neurologic disability and prevention of clinical progression or recurrence with the least morbidity. Recent advances in skull base surgical techniques, through an appreciation of skull base anatomy and institutional specialization, have contributed major improvements to the outlook for patients with these tumors, and previously inoperable cases may now often be removed completely with acceptable risk. Since significant morbidity may be incurred during surgical resection of these difficult lesions, especially in terms of cranial nerve dysfunction, the value of aggressive surgical resection must be weighed against the often indolent natural history of these lesions, and must be individualized in each patient. Completeness of resection is the major prognostic factor determining the out-come of patients with typical benign meningiomas in terms of length of survival, risk of recurrence, and neurological disability. Various means of prognosticating the growth potential of a given tumor are being investigated, though none have yet been confirmed for their predictive value in typical, histologically benign meningiomas. The role of external beam radiotherapy has not been subjected to adequately controlled, prospective studies, and there is currently insufficient followup to assess the risks and benefits of stereotactic radiosurgery.Advances in the clinical management of tumors of the skull base has had perhaps the greatest impact for patients with meningiomas who constitute a large portion of tumors seen in these locations. Although the majority have benign histological features, skull base meningiomas can present a formidable challenge due to their proximity to vital structures, surgical inaccessibility, and occasional aggressive features. The combination in recent years of advances in skull base surgical techniques, adjuvant therapy, and rehabilitation methods have dramatically improved the outcome for these tumors.     

Radiosurgery of Benign Lesions

The use of stereotactic radiosurgery is increasing at an accelerated rate throughout the United States and the rest of the world. The greatest success for radiosurgery has been in the treatment of benign intracranial mass lesions and arteriovenous malformations (AVM) in particular. The majority of large radiosurgery series report that AVM obliteration rates exceed 74% and serious complication rates (permanent brain injury) exceed less than 5%. Radiosurgery is being investigated as a treatment for high-risk angiographically occult vascular malformations (cavernous angiomas) with a history of hemorrhages, but is contraindicated in asymptomatic patients. Radiosurgery has been successfully established as an alternative to surgical resection of vestibular schwannomas (acoustic neuromas). Long-term tumor control rates with radiosurgery are above 85%. Radiosurgery offers tumor control comparable to surgery with better preservation of hearing and facial nerve function. Radiosurgery has also been found to be equally effective in controlling nonacoustic schwannomas and meningiomas. Radiosurgery offers the potential of faster and higher response rates in treating functional pituitary adenomas than fractionated radiotherapy with a greater chance of preserving normal pituitary function. Long-term studies with 10 to 15-year follow-up are still needed to fully compare the efficacy of radiosurgery with other modern techniques for treating pituitary adenomas and meningiomas (such as cranial base microsurgery and fractionated large-field radiotherapy). Overall, radiosurgery is a relatively safe and effective alternative to surgical resection of small AVMs and most benign intracranial tumors.     

The Evolving Role of Stereotactic Radiosurgery for Patients with Skull Base Tumors

Tumors located at the base of the skull are among the most difficult problems that neurosurgeons encounter. Management of patients with skull base tumors must take into account that complete tumor removal is not possible with acceptable morbidity in many patients. Therefore, radiation therapy and stereotactic radiosurgery are commonly performed. The use of radiosurgery for patients with skull base tumors has increased significantly over the past three decades and we now possess a better understanding of the expectations of skull base radiosurgery. For properly selected patients with benign tumors (meningiomas, schwannomas, glomus tumors), tumor control rates between 90 and 100% have been reported. Local control rates for chordomas and chondrosarcomas have ranged from 50 to 70%, but tumor growth adjacent to the treated area (marginal failure) remains a significant problem. Radiosurgery is also commonly performed for patients with malignant skull base tumors as a palliative treatment and symptom relief is common, especially for patients with facial pain related to their tumor. Follow-up beyond 10 years is still needed to better define long-term results of radiosurgery and the incidence of radiation-induced neoplasms after radiosurgery.     

Stereotactic radiosurgery for WHO grade I meningiomas

Meningiomas represent a common intracranial tumor in the adult population. Although extirpation to achieve a gross total resection or at least decrease mass effect has been the mainstay of treatment, stereotactic radiosurgery has come to play an increasingly important role in the management of patients with meningiomas. Radiosurgery utilizes highly focused, beams of ionizing radiation to inactivate tumor cells. Image guidance and a steep dose fall off are critical features of this approach. The radiobiology of radiosurgery differs in certain advantageous ways from conventional radiotherapy. Radiosurgery initially was utilized to treat recurrent or residual skull base meningiomas. As success was observed in this setting, radiosurgery has gradually expanded its role so as to treat convexity meningiomas; it is also used as an upfront treatment for patients for whom clinical and neuro-imaging findings are consistent with a meningioma. Most large series demonstrate tumor control rates for patients with grade I meningiomas in excess of 85%. Neurological function is generally preserved or improved for patients with meningiomas. However, complications can occur. Longitudinal follow-up including neurologic and radiologic assessment is required. Single and multisession stereotactic radiosurgery will likely play an expanded role in the treatment of patients with meningiomas.     

Linear accelerator based radiosurgery as a salvage treatment for skull base and intracranial invasion of recurrent nasopharyngeal carcinomas

Nasopharyngeal carcinoma is a common disease entity in Taiwan. It can spread in the prestyloid, retrostyloid compartments, parapharyngeal space, and skull base, and induce paralysis of cranial nerves. We have treated more than 1,500 cases in the past 14 years. Since 1994, we have treated 11 cases of nasopharyngeal carcinomas with skull base invasion by linear accelerator-based stereotactic radiosurgery. There were six male and five female patients. The mean age was 48.4 years. Seven patients had symptoms of low cranial nerves. For these patients, conformal radiotherapy plus brachytherapy was used for the masses beyond the skull base. Stereotactic radiosurgery with a dose of 10 Gy to 19 Gy for one treatment was used for the masses invading the skull base. Eight patients died in follow-up periods from 5 months to 2 years 7 months. Approximately half of patients revealed good response of tumor to radiosurgery. Two patients demonstrated no response of tumors to radiosurgery. Stereotactic radiosurgery may be an adjuvant treatment for recurrent nasopharyngeal carcinomas with skull base and intracranial invasion.     

Linear Accelerator-Based Radiosurgery in the Management of Skull Base Meningiomas

From May 1994 to December 1999, 43 patients with meningiomas in the base of the skull underwent linear accelerator (LINAC)-based stereotactic radiosurgery (SRS) at Chung Gung Memorial Hospital. SRS was performed as a primary treatment in 14 patients, and after resection in 29 patients. The mean tumor volume was 5.68 cc, and the mean target surface dose was 16 Gy, delivered with an average of three isocenters. The median follow-up was 74.5 months. The 7-year local control rate and 7-year overall survival rate were 89.7% and 80.2%, respectively. The 7-year local control was 100% and 84.4% in SRS alone group and surgical excision with SRS group (p = 0.21), respectively. A stationary tumor following SRS was seen in 23 (53.5%) patients, partial shrinkage was seen in 16 (37.2%) patients, and complete disappearance in one patient was seen (2.3%). Furthermore, disease progression was noted in three (7%) patients, one of whom died of disease. The median time to tumor response was 15.4 months (range 5.8-52.8 months). Cases remained stable or had improved neurological statuses without any deterioration in 37.9% and 78.7% of the groups treated with surgery and SRS and SRS alone, retrospectively. In summary, LINAC-based SRS is an effective and safe modality of treating unresectable or partially resected meningiomas in the base of the skull. For tumors with diameters of 3 cm or less, particularly in patients without or with minimal clinical neurological symptom, SRS alone can provide a good local control without causing cranial neuropathy.     

Adjuvant radiotherapy for atypical and malignant meningiomas: a systematic review

Atypical meningiomas (AMs) and malignant meningiomas (MMs) are tumors with a lower incidence and poorer prognosis than benign meningiomas. The role of radiotherapy as an adjuvant to surgical resection, especially for AMs, is incompletely defined. In this study, the English-language literature was systematically reviewed for studies that reported tumor characteristics, treatment parameters, and clinical outcomes after adjuvant radiotherapy for AM and MM, including overall survival, progression-free survival, and/or time to recurrence or mortality. Clinical outcomes were further assessed in the context of resection status, timing of administration, and radiation dose. Outcomes after stereotactic radiosurgery were also examined. Treatment toxicity and other potential prognostic or confounding factors were appraised. Ten and 11 studies for AM and MM, respectively, met the inclusion criteria. The median 5-year progression-free survival and overall survival after adjuvant radiotherapy were 54.2% and 67.5%, respectively, for AM and 48% and 55.6% for MM. The complication rates were 11.1% for AM and 5.1% for MM. Incomplete resection and radiation dose <50 Gy conferred significantly poorer 5-year progression-free survival. Most studies were unable to demonstrate a statistically significant prognostic benefit for adjuvant radiotherapy in AM. In conclusion, adjuvant radiotherapy significantly improved local control of AMs and MMs, especially after subtotal resection. Study limitations, including inadequate statistical power, may underlie the studies'' inability to demonstrate a statistically significant benefit for adjuvant radiotherapy in AM. Because these tumors preferentially recur within 5 years of surgical resection, future studies should define whether early adjuvant therapy should become part of the standard treatment paradigm for completely excised tumors.     

Stereotactic radiosurgery provides equivalent tumor control to Simpson Grade 1 resection for patients with small- to medium-size meningiomas

PURPOSE: To compare tumor control rates after surgical resection or stereotactic radiosurgery for patients with small- to medium-size intracranial meningiomas. MATERIALS AND METHODS: Between 1990 and 1997, 198 adult meningioma patients treated at our center underwent either surgical resection (n = 136) or radiosurgery (n = 62) as primary management for benign meningiomas <35 mm in average diameter. Tumor recurrence or progression rates were calculated by the Kaplan-Meier method according to an independent radiographic review. The mean follow-up was 64 months. RESULTS: The tumor resections were Simpson Grade 1 in 57 (42%), Grade 2 in 57 (42%), and Grade 3-4 in 22 (16%). The mean margin and maximal radiation dose at radiosurgery was 17.7 Gy and 34.9 Gy, respectively. Tumor recurrence/progression was more frequent in the surgical resection group (12%) than in the radiosurgical group (2%; p = 0.04). No statistically significant difference was detected in the 3- and 7-year actuarial progression-free survival (PFS) rate between patients with Simpson Grade 1 resections (100% and 96%, respectively) and patients who underwent radiosurgery (100% and 95%, respectively; p = 0.94). Radiosurgery provided a higher PFS rate compared with patients with Simpson Grade 2 (3- and 7-year PFS rate, 91% and 82%, respectively; p <0.05) and Grade 3-4 (3- and 7-year PFS rate, 68% and 34%, respectively; p <0.001) resections. Subsequent tumor treatments were more common after surgical resection (15% vs. 3%, p = 0.02). Complications occurred in 10% of patients after radiosurgery compared with 22% of patients after surgical resection (p = 0.06). CONCLUSIONS: The PFS rate after radiosurgery was equivalent to that after resection of a Simpson Grade 1 tumor and was superior to Grade 2 and 3-4 resections in our study. If long-term follow-up confirms the high tumor control rate and low morbidity of radiosurgery, this technique will likely become the preferred treatment for most patients with small- to moderate-size meningiomas without symptomatic mass effect.     

Linac radiosurgery for benign meningiomas

PURPOSE: To review outcomes for patients treated with linac radiosurgery for benign meningiomas. METHODS AND MATERIALS: Between January 1989 and July 1997, 70 patients with 76 meningiomas were treated with LINAC-based radiosurgery. In 38 patients, radiosurgery was the initial treatment. In 32 patients, radiosurgery followed surgery or conventional radiotherapy. The average treatment volume was 10.0 cm3 (range, 0.6 to 28.6 cm3). The mean peripheral dose was 12.7 Gy (range, 10 to 20 Gy). The mean clinical follow-up period was 23 months. No patient was lost to follow-up. RESULTS: No lesions enlarged during the follow-up period; of 48 lesions in patients who had follow-up for at least one year and hence had follow-up imaging, 27 tumors remained unchanged and 21 tumors were reduced in size. Two patients experienced transient radiation-induced neurological deficits. One was treated with surgical excision of the tumor; the other responded to prolonged steroid therapy. Both patients, treated early in our experience, received doses higher than we would currently recommend. CONCLUSIONS: Early results suggest that stereotactic radiosurgery is an effective treatment for meningiomas. Long-term follow-up will be necessary to fully evaluate its efficacy.     

The CyberKnife®

Stereotactic radiosurgery has emerged as an accepted treatment for many types of intracranial tumors. Based on the understanding of the limitations of prior radiosurgical systems, image-guided robotic radiosurgery was developed to overcome many of these restrictions. The CyberKnife® is a commercially available frameless image-guided radiosurgical system that provides state-of-the-art radiosurgery for intracranial tumors, and has also revolutionized the use of radiosurgery to treat tumors in other parts of the body. This review focuses on the current use of the CyberKnife® to treat cranial and spinal tumors. Brain metastases have long been treated with other radiosurgical systems, but the CyberKnife® allows patients with brain metastases to be treated multiple times as successive tumors are discovered, without the repetitive placement of a stereotactic head frame. Benign tumors such as acoustic neuromas, pituitary tumors, and meningiomas are also easily treated with the CyberKnife®, with radiographic tumor-control rates of >90% for pituitary tumors and 95% for acoustic neuromas and meningiomas. A subset of meningiomas and pituitary tumors surround the optic nerves and are considered to be perioptic tumors. Historically, these tumors have not been treatable with radiosurgery because of the risk of visual loss. The frameless nature of the CyberKnife® allows the radiosurgery treatment to be delivered in separate stages (typically 24 hours apart); this has been shown to significantly reduce the risk of visual loss, and thus allows effective radiosurgery treatment to be delivered. Staged radiosurgery treatment has also been used at our institution to treat acoustic neuromas, with the understanding that several stages of radiation delivery may be associated with a higher level of hearing preservation than a single-staged radiosurgery treatment. Malignant gliomas and nasopharyngeal carcinoma tumors have historically been treated with conventional radiotherapy techniques. However, we have learnt that supplementing these radiotherapy treatments with a CyberKnife® stereotactic boost after radiotherapy can improve response rates to treatment. Spinal radiosurgery is a novel development; prior frame-based radiosurgery devices did not allow treatment of lesions outside the brain and neck. We have observed high rates of tumor control when treating benign spinal tumors with the CyberKnife®, and have noted excellent pain relief and tumor-control rates in patients with spinal metastases. Future CyberKnife® stereotactic applications will focus on the continual expansion of this technology to treat tumors outside the CNS, including cancers of the lung, pancreas, liver, and prostate.     

CyberKnife stereotactic radiosurgery for intracranial neoplasms, with a focus on malignant tumors

Stereotactic radiosurgery is well established as a means of managing intracranial tumors, both as an adjuvant to surgical resection, and also as a primary treatment modality for those tumors that are considered unresectable by conventional surgical means. Of particular concern during radiosurgery of brain tumors is the risk of radiation damage to otherwise healthy tissue, potentially resulting in cognitive impairment. The conformality and precise targeting of the CyberKnife radiation beam enables this risk to be minimized to a greater extent than hitherto possible, which may allow treatment to be completed in a small number of fractions, thereby improving the quality of life for patients. The CyberKnife has proven particularly valuable in the treatment of metastases, which represent the great majority of brain tumors, though its role in the management of malignant glial tumors remains a subject of controversy. This article reviews the published studies on the efficacy of CyberKnife radiosurgery for brain tumors of both glial and metastatic origin, and considers its future role in the management of such lesions.     

Management of Meningeal Neoplasms: Meningiomas and Hemangiopericytomas

Meningiomas are the most frequently diagnosed primary brain tumor accounting for nearly one third of all primary brain and central nervous system tumors reported in the United States. According to the 2007 World Health Organization classification scheme, Grade I meningiomas are benign, Grade II defines atypical lesions, while Grade III meningiomas are anaplastic or frankly malignant tumors. Not surprisingly, Grade II and III meningiomas usually follow a more aggressive course and confer a worse prognosis. The diagnosis of meningioma is confirmed by pathologic examination and improvements in imaging help to better define when observation versus intervention is appropriate. Surgical resection, when possible, is the mainstay of treatment. When complete resection is not possible, stereotactic radiosurgery (SRS) can result in disease stabilization. Chemotherapy has yet to result in reproducible long-term disease free or overall survival benefits. Biologic agents remain under investigation. Hemangiopericytomas are rare dural based sarcomas. These tumors are known for their aggressiveness, high recurrence rates and their proclivity to metastasize to extracranial locations. Gross total resection when feasible remains the treatment of choice.     

Skull Base Surgery for Benign Skull Base Tumors

The use of skull base techniques in the treatment of benign skull base tumors has allowed access to areas of the brain once considered inaccessible. The most common benign skull base tumors encountered in neurosurgical practice are benign meningiomas, schwannomas, and glomus jugulare tumors. Gross total resection of these lesions gives patients the best possible chance of a cure. In this paper, we review the rationale for the use of skull base surgery techniques for benign skull base tumors.     

Skull Base Surgery for Benign Skull Base Tumors

The use of skull base techniques in the treatment of benign skull base tumors has allowed access to areas of the brain once considered Inaccessible. The most common benign skull base tumors encountered in neurosurgical practice are benign meningiomas, schwannomas, and glomus jugulare tumors. Gross total resection of these lesions gives patients the best possible chance of a cure. In this paper, we review the rationale for the use of skull base surgery techniques for benign skull base tumors.     

Defining the role of radiosurgery in the management of brain metastases.

The role of stereotactic radiosurgery in the management of recurrent and newly diagnosed brain metastases was evaluated prospectively. From December 1988 to March 1991, 58 lesions in 40 patients were treated with accelerator-based stereotactic radiosurgery. All patients were followed for a minimum of 6 months or to death. The primary purpose was to determine the impact of radiosurgery on local control and its subsequent effects on quality of life. An overall tumor control rate of 82% with a complete response rate of 43% were achieved. As anticipated, the response rate for smaller tumors was substantially better than that for larger tumors (78% for lesions < 2 cm3; 50% for lesions > or = 10 cm3). Although the overall in-field progression rate was 18.5%, only 1/23 (4%) complete responders subsequently recurred. The in-field failure rate is highly comparable with recently published surgical data. Progression outside the brain was noted in two-thirds of patients. One quarter of the deaths were neurologic. The median survival for this minimally selected patient population was 6.5 months. Stereotactic radiosurgery was also associated with improved quality of life as measured by Karnofsky score, neurologic function, and steroid dependence. Long-term steroid dependence was encountered in only four patients. We conclude that stereotactic radiosurgery can be used effectively in patients with brain metastases. In this series, a high tumor response rate was achieved which was associated with improved quality of life.     

颅底良性肿瘤立体定向放射外科治疗

 目的 探讨颅底良性肿瘤的SRS治疗效果。方法 1994 年7 月至1996 年12 月对22例（23 个肿瘤） 手术后残存或者复发的颅底良性肿瘤实施了SRS治疗。结果 治疗后大多数病人（1822） 的临床症状获得改善,无治疗相关的永久性颅神经损伤发生。影像学观察提示有9 个肿瘤体积缩小,13 个肿瘤体积无变化,1 例肿瘤增大。有813 例（61-5 % ） 神经鞘瘤病变中心表现出CT影像的低密度。结论 对经过选择的颅底良性肿瘤实施SRS治疗,可以获得良好的局部肿瘤控制效果和比较低的治疗并发症。     

Stereotactic radiosurgery for intracranial chondrosarcoma

To assess outcomes after stereotactic radiosurgery (SRS) for chondrosarcomas of the skull base, we reviewed 22 patients with cranial base chondrosarcomas who underwent SRS between 1987 and 2009. The median patient age was 42 years (range, 15-75). The median SRS target volume was 8.0 cc (range, 0.9-28.2) and median margin dose was 15.0 Gy (range, 10.5-20). 15 patients (68 %) underwent one or more tumor resections and 3 of these patients also had fractionated radiation therapy. At a median follow-up of 75 months after SRS, seven patients died due to tumor progression. The actuarial overall survival after SRS for the entire group of chondrosarcoma patients was 95, 76, 70 and 56 % at 1, 3, 5 and 10 years, respectively. Factors associated with longer survival after SRS included patient age >40 years, a shorter interval (<6 months) between diagnosis and SRS, and either no or a single prior resection. Treated tumor control rates were 91, 72, 72 and 54 % at 1, 3, 5 and 10 years, respectively. Factors associated with longer progression-free survival after SRS included patient age >40 years and no prior RT. Symptomatic adverse radiation effects occurred in two patients (10 %). Stereotactic radiosurgery may provide a benefit to patients as either a primary or adjuvant therapy. The ability to achieve tumor control in patients with chondrosarcoma is likely to be enhanced by earlier timing of SRS after diagnosis and multimodal management, beginning with resection when feasible followed by early SRS for progressive residual tumor.     

Radiotherapy for meningiomas

Because of a substantial overall recurrence rate of meningiomas, the role of surgery as the sole treatment for every case must be evaluated. Also, occasionally, the patient's age and/or the location of the tumor precludes considering him/her as a candidate for surgery. In these instances, radiotherapy or radiosurgery may be advisable. The article presents two cases treated at M. D. Anderson Cancer Center, those of a 65-year-old male with a tumor in the left temporal lobe and 74-year-old female with a tumor in the right petroclival region. It also reviews the roles that radiotherapy plays in treating patients with meningiomas. Retrospective analyses of outcomes provide ample evidence that conventional radiation after incomplete resection reduces the incidence of progression of tumor over a long period. Information on patients who have had only external radiation is meager, since most patients have at least a partial resection. Complete resection for benign meningiomas is sufficient. For malignant meningiomas, adjuvant radiation should be administered, regardless of the extent of surgical excision. When surgery poses a high risk of morbidity or mortality, radiation therapy and radiosurgery are promising alternatives.     

Radiothérapie stéréotaxique des méningiomes intracrâniens

Meningiomas are the most common non-malignant tumours of the brain. Gross-total resection remains the preferred treatment, if achievable without morbidity. Radiation therapy is advocated for inoperable, incompletely resected, or recurrent grade 1 tumours, if there is a progressive, symptomatic lesion, or in case of functional impairment. Postoperative radiation therapy is recommended for grade 2 or 3 lesions. Fractionated stereotactic radiotherapy and stereotactic radiosurgery are high precision techniques, allowing good sparing of surrounding tissues. Fractionated stereotactic radiotherapy and stereotactic radiosurgery give comparable results, with excellent 5-year tumour control rates of more than 90% for benign meningiomas. Toxicity is low and seems equivalent, despite a biased use of fractionated stereotactic radiotherapy for larger meningiomas, close to critical structures. Fractionated stereotactic radiotherapy seems to be of special interest in the treatment of cavernous sinus or optic pathways meningiomas. The different therapeutic modalities should be discussed by a multidisciplinary team.